<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .show{
            height: 0px;
            width: 100px;
                 }

         .hide{
             width: 100px;
             height: 0;
             opacity: 0;
             visibility: hidden;
             transition: 2s;
        }
        .show:hover .hide{
            visibility: visible;
            height: 100px;
            opacity: 1;
            background-color: red;
        }
    </style>
</head>
<body>
<div class="show">
    显示图片
    <div class="hide">
    <div>1</div>
        <div>2</div>
        </div>
</div>
</body>
</html>